1. Field
This document relates to modulating and detecting a mark within a content signal for signaling purposes.
2. Description of the Related Art
Motion picture and television broadcast studios (the “studios”) and their affiliates are in the business of producing, manufacturing and/or distributing copyrighted content including motion pictures and television shows. The studios, either directly or through their affiliates, distribute motion pictures and television shows via television transmission, theatrically, and on videocassette tapes and digital versatile discs (“DVDs”).
The copyrighted content of the studios is subject to both authorized and unauthorized reproduction. In an effort to protect its copyrighted content, the studios have implemented a number of copy protection schemes to limit the type and amount of unauthorized reproduction. For example, content scramble system (CSS) was implemented to prevent digital copying of protected DVDs and Macrovision's technology was implemented to prevent unauthorized copying of copyrighted video tapes by use of a carefully timed sequence of protection pulses that upsets the video auto gain control and the horizontal synch.
The studios recently sought a suitable content protection system to protect copyrighted content that has been copied by taking the content in its current format (e.g., digital or analog video), playing it on a playback device through an analog output and capturing the analog signal in an analog or digital format so that the content can be reproduced without restriction. The potential for copying content via an analog output in an unrestricted manner is commonly referred to as the “analog hole”.
Copy Generation Management System—Analog (“CGMS-A”), was adopted by the studios as a partial solution to the analog hole. CGMS-A inserts a transport carrying copyright information in the vertical blanking interval (VBI) of a video signal. The copyright information has four associated states: (1) a “copy never” state indicating that the content can never be copied, (2) a “copy once” state indicating that the content can be copied, but that the newly copied content cannot be further copied, (3) a “copy no more” state indicating that the content is a copy from content designated with a copy once state and can therefore no longer be copied, and (4) a “free to copy” state indicating that the content is not subject to copy restrictions. Since video signals predated CGMS-A, by default unencoded content is interpreted by a CGMS-A system as being in a “free to copy” state.
The studios recognized that CGMS-A was not a panacea to resolving the analog hole. In response, the studios launched, through the Copy Protection Technical Working Group, an analog reconversion discussion group with representation from the consumer and electronics industry to actively seek a solution to the analog hole.